WASHINGTON -- ​Prime Minister Benyamin Netanyahu waxed broadly of a Middle East in turmoil on Sunday, in his first public comments on the threat posed to the region by ISIS, a terrorist militia conquering swaths of territory in eastern Syria and northern Iraq.

Threatening a borderless conflict between "extremist Shi'ites," funded by leadership of the Islamic Republic of Iran, and equally extreme Sunnis— a soft "alliance" between ISIS and al Qaeda— the Israeli prime minister suggested the United States should largely stay out of the fight, and instead allow the parties to weaken one another.

"Don't strengthen either of them. Weaken both," Netanyahu said.

As US President Barack Obama weighs precise air strikes against the Sunni terrorist group, which seeks to establish an Islamic caliphate across Iraq and the antiquated al-Sham lands, Netanyahu declined to comment on the wisdom of direct intervention.

He instead pivoted to what he characterized as the larger threat to the region: Iran's acquisition of a nuclear weapons capacity, or a "bad deal" between Iran and the international community that would preserve major components of its nuclear program.

Western diplomats working to end the nuclear crisis should fashion a deal with Iran similar to an agreement reached last fall, brokered by Russia and the US, that rid Syria's President Bashar Assad of his massive chemical weapons stockpile, Netanyahu said, calling the Syrian accord a "good deal."

World powers are currently negotiating with Iran in Vienna towards a comprehensive solution to the crisis. The US, Israel and its allies suspect Iran's nuclear program has military dimensions.